Wrinkling Modes and Instabilities in Elastomers and Film/Elastomer Bilayers

John W. Hutchinson
School of Engineering and Applied Sciences
Harvard University

Recent research activities in soft materials have generated a rich array of new experimental and theoretical observations on wrinkling modes of compressed single-layer elastomers and bilayers comprised of a stiff thin film on a thick compliant elastomer substrate. The seminar will begin with a presentation of examples drawn from experimental work by a number of investigators. Then, an overview will be presented of recent theoretical work describing different kinds of wrinkling modes and their stability with emphasis on both initial wrinkling modes and secondary modes that arise as the compression is increased well beyond the onset of wrinkling. Advanced modes such as folds, creases and mountain ridges will be described. Contrasts between single-layer and bilayer behaviors will be drawn. In particular, the exceptional stability of the sinusoidal wrinkling mode of a stiff thin film on a compliant substrate is contrasted the highly unstable and imperfection-sensitive behavior of wrinkling of a compressed half-space of elastomer. Wrinkling of a compressed elastomer half-space is highly unstable due to nonlinear interaction among the multiple modes associated with the critical compressive state. Half-space surface wrinkling is a pathway leading to an alternative surface instability mode, the finite amplitude crease--the crease can be regarded as the collapsed state of the wrinkle.